Circular knitting-machine

ABSTRACT

The needles of a knitting machine are selectively actuatable upon passing by electro-magnetic selection members. A tape carrying a program for controlling selection of the needles is driven past a reader which supplies information in the form of electrical signals to a memory. The signals are extracted from the memory at the frequency of passage of the needles past the selection members, and supplied to the selection members to select the needles. The speed of driving the tape is servocontrolled as a function of the quantity of information in the memory whereby the rate of reading information on the tape need not be synchronized with the frequency of passage of the needles past the selection members. This facilitates use of a two-ended tape alternately wound and unwound from one spool to another. The tape can also carry information for controlling reversal of tape driving means and for selectively reading the principal information according to the direction of motion thereof.

United States Patent Bourgeois (4 1 June 20, 1972 s41 CIRCULAR KNITTING-MACHINE 3,446,037 5/1969 Sutton ..66/ [72] Inventor: Norbert Pm] no I Troyes. Frame 3,470,714 10/1969 Corbaz ....66/$0 R [73] Assignee: Etudes e1: Bonneterle SA, Lausanne, Swit- FOREIGN PATENTS 0R APPLICATIONS wland 1,917,574 11/1969 Germany ..66/50 a [22] Filed: July 24, 1970 Primary Examiner-Wm. Carter Reynolds [2]] Appl' 57980 Anomey-Wenderoth, Lind 8a Ponack Foreign Application Priority Data ABSTRACT July 31, 1969 France ..69263l9 The needles of a knitting machine are selectively actuatable July 31, 1969 France ..6926320 upon passing by electro-magnetic selection members. A tape carrying a program for controlling selection of the needles is [52] US. Cl ..66/ R, 66/1 54 A driven past a reader which supplies infonnation in the form of [51] Int. Cl. ..D04h 15/78 electrical signals to a memory. The signals are extracted from Field 0| sell'ch 174-1 174-! the memory at the frequency ofpassage ofthe needles past the 179/100-2 Ml; 235/15 1; 66/25 50 50 1 154 selection members, and supplied to the selection members to A select the needles. The speed of driving the tape is servo-controlled as a function of the quantity of information in the [56] Rdmnm Cm memory whereby the rate of reading information on the tape UNITED STATES PATENTS need not be synchronized with the frequency ofpassage of the needles past the selection members. This facilitates use of a 3,561,232 2/1971 Stock et a1. ..66/50 R two-ended tapg alternately wound and unwound from one 3.566.090 2/1971 Johnson-m 172-5 X spool to another. The tape can also carry information for con- 3 4/1967 Smclf A trolling reversal of tape driving means and for selectively read 3,016,522 I/ l 952 Loulle et 340/174-1 H ing the principal information according to the direction of mo- 3,047,868 7/1962 Schrimpf .340/174 1 H th f 3,088,101 4/1963 Schrimpf ..340I174.1 H 2,904,777 9/1959 Cox et a] ..340/174. I H 9Clalnm, 7 Drawing Figures P'A'TENTEDJUH 2 0 m2 SHEET 10? 5 NORBERT PAUL BOURGEOIS,

wwmazvm Attorneys PATENTEDJUH20 m2 SHEET 3 BF 5 NORBERT PAUL BOURGEOIS,

Attorneys PATENTEDJUM 20 1972 SHEET Q [If 5 NORBERT PAUL BOURGEOIS,

I By, W1 i 1 Attorneys CIRCULAR KNITTING-MACHINE BACKGROUND OF THE INVENTION It is commonplace in the textile industry, and in particular in the knitting industry, to utilize programs having bits of information stored in a given order to control various operations of a knitting machine, for example control of the selection of the needles or other knitting accessories associated therewith.

These programs can be elaborated on various types of carriers, such as jacquard cards, tapes, films and so on, on which the information is recorded in relief, by punching, by optical or magnetic recording, or in any other suitable manner.

Scanning of the information is carried out during operation of the knitting machine, by a relative displacement between the program and information readers. Corresponding orders are then transmitted by mechanical transfer means or by electrical signals to selecting members fixed to the cam-box of the knitting machine. The elements are thus selectively influenced as they move past the selecting members.

In certain known systems, the programs consist of an endless tape which moves continuously past information scanning means or readers; the orders emitted by the reader are then transmitted to the elements to be selected by the intermediary of mechanical or electro-mechanical means.

The major part of an endless tape of this kind is generally wound up to form an annular spool enclosed within a support casing. The convolutions of the spool are generally guided by rollers, and the remaining loop passes over a driving device the rotation of which is accurately controlled by operation of the knitting machine and which pulls the outer convolution while pushing the inner convolution, or vice-versa.

Experience has shown that this method of driving and winding up could be usefully employed for program tapes such as metallic films, the elastic flexibility and relative rigidity of which favors winding in a spiral.

The development of certain very supple materials enables the practical and economic production of program tapes, such as tapes in plastics material, cinematographic films, and so on, upon which it is possible to store information either in the form of perforations, or in the form of optical or magnetic recordings, or otherwise.

The lack of rigidity, the low elasticity and the relative fragility of these materials, which cannot normally be subjected to control by a pushing movement, has led to the development of quite different winding techniques.

Hence, in certain systems, the greater part of an endless ta e is stored in a guide housing in the form of zig-zag loops.

Other types employ a two-ended information-carrying program tape, driving and winding devices being provided to alternately wind this tape from one end to the other so that during the alternating motion of the tape the information is read by scanning means in the path of the tape.

Continuous reading of the information poses no major problems in the case of endless tapes, but the same is not true for two-ended tapes for which it is necessary to take into account the dead time required for reversal of the direction of motion.

This requirement necessitates the provision of relatively complex accessories, which are difficult to integrate with rapidly operating knitting machines, in particular for circular knitting machines for which control of the selection of the needles or associated knitting accessories must necessarily be carried out continuously.

To obtain a precise individual selection of the elements to be controlled, it is indispensable that the orders emanating from reading of the information on the program are transmitted to the selecting members at a frequency strictly identical to the frequency of the movement of these elements past the selecting members.

This result cannot be achieved solely by the use of reliable mechanisms which eliminate slip; despite taking strict precautions, it is found that staggering between the driving members of the knitting machine and the mechanism of the pro- Rmmming devioe arises, and it is not always remedy the situation.

The control of these programming devices is thus directly related to the operation of the knitting machine and the users must consequently conform to certain requirements, the most important of which is to ensure the regularity of spacing of the bits of information on the program when the program is made.

While it is possible, by using appropriate synchronization means, to carry out certain limited corrections, these types of device controlled by the knitting machine necessitate that a close relationship is established between a) the surface of the program scanned by the readers in a given period of time and (b) the number of elements to be selected concerned by the bits of information on the scanned stu'face and which must be accurately selected in the same period of time.

Particular attention must thus be accorded to the arrangement of the information on such programs which, for the control of the individual selection of the needles of certain largecapacity jacquard circular knitting machines, must store several hundreds of thousands of bits of information which are transmitted in the form of control signals to the selected members at a frequency which can exceed 600 signals per second.

SUMMARY OF THE INVENTION The invention concerns a circular knitting machine comprising a plurality of elements to be controlled movable past at least one selecting member. According to the invention, means for selectively actuating each selecting member comprise a tape carrying a program of information, means for driv ing the tape along a path and for winding the tape, reading means adjacent the path of the tape, means for storing the information from the reading means, means for extracting information from the storage means in the order of reading at a frequency equal to the frequency of passage of elements past each selection member and for transmitting this information to the selecting member(s), means for quantitatively comparing the input of information to the storage means with the output of information from the storage means, and means for regulating the tape driving means as a function of the quantity of information in the storage means so that the speed of driving of the tape and consequently the rate of reading information on the tape need not be synchronized with the frequency of of the elements past each selecting member.

In this knitting machine, operation of the reading means for the program tape is not directly subordinated to the movement of the mechanisms controlling the operation of the knitting machine: this enables the program to be produced without having to provide for a regular spacing of a given quantity of information per unit length of tape, and it is not necessary during operation of the knitting machine to read the information at a rate directly related to the frequency of movement of the elements to be selected past the selecting members.

possible to easily DESIGNATION OF THE DRAWINGS.

The accompanying drawings show, by way of example, two embodiments of the knitting machine according to the invention.

FIG. 1 is an overall schematic view of a knitting machine with a program tape device, only the parts concerning the invention being shown.

FIGS. 2 and 3 are respectively schematic fi-ont and side views of the principal elements for alternately driving and winding the program tape device of FIG. 1.

FIG. 4 is an overall schematic view of a knitting machine with a modified program tape device; as in FIG. 1, only the parts of interest to the invention are shown.

FIGS. 5 and 6 are respectively a side view an elevation, partly in cross-section along line A-A of FIG. 5, of details of FIG. 4.

FIG. 7 schematically shows, on an enlarged scale, the arrangement of bits of information on a program tape which can be read in the two directions of movement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The circular knitting machine of FIG. 1 comprises a needle cylinder 1 at the periphery of which are a series of axial grooves 2 in which independent needles 3 each with an associated needle-jack 4 can slide. The jacks comprise actuating butts which can cooperate with the cams (not shown) of a stationary annular cam-box 6. The cylinder 1 is rotatably driven by means of a toothed crown 43 fixed thereto.

The jacks 4 can be actuated at a plurality of selection stations by selective excitation of electro-magnetic selecting members 7, 7a, 7b, and so on, fixed to the stationary cam-box 6. At each selection station, the jacks are either selected, in which case the jacks and associated needles are raised by means of a raising cam to an operative position, or nonselected, in which case the jacks and associated needles remain in a lowered non-operative position.

The knitting machine also comprises a program device com prising a tape or film 8 the two ends of which are attached to the hubs 9 of winding members such as spools 10 (FIGS. 2 and 3) connected to electro-magnetic clutches 11 and 12. Instead of having two ends, the program tape could alternatively be of the endless type.

The film 8 has a plurality of longitudinal information tracks 13 each carrying information for one of the selecting members 7 of the knitting machine in the form of transparent or opaque zones. Additionally, the film has an auxiliary track 36 carrying pilot information in a similar form and which effectively divides the film into a plurality of transversal lines of infonnation across each of the information tracks 13.

On either side of the tracks 13, the film 8 has driving perforations 14 which mesh with sprockets 15 of driving drums l6 and 17. These drums are driven by cogwheels l8 and 19 fixed thereto and which are themselves driven by a cog wheel 20 which is in turn driven by cog wheels 21 and 22 by a D.C. motor 23 connected to a power source by wires 24 and 25.

The electro-magnetic clutches 1] and 12 are connected to the drive mechanism by a cog wheel 26, pulleys 27, 28 and 29, and a band 30. Clutches 11 and 12 each have a mobile part, 3] and 32 respectively, which rotationally drives the winding member associated therewith when the corresponding clutch coil is excited. In FIG. 3, part 32 is shown in the excited (driving) position while part 31 is shown in the non-excited position.

The direction of rotation of the motor 23 can be reversed, thereby reversing the direction of rotation of the electro-magnetic clutches 11 and 12, either as an independent operation or as a function of the number of bits of information provided on a length of the film 8. In the latter case, the film 8 carries special reversing information, not shown.

The reading of the infonnation on the film 8 and the servocontrol of the speed of the D.C. motor 23 are carried out in the following manner:

A stationary reading device 33 comprising one individual reader per track of the film is located over the film 8 between the driving drums 16 and 17. During motion of the film 8, the individual readers successively detect information on the above-mentioned transversal lines of information. The information from the readers associated with the information tracks 13 is fed as signals in the form of electrical impulses, schematically indicated by continuous lines 13a, 13b, and so on, to one or more memories 34 with a dynamic displacement register for temporarily storing this information.

Simultaneously, another of the individual readers of the reading device 33 associated with the auxiliary track 36 feeds pilot signals to the memory 34 in the form of electrical impulses schematically represented by a dashed line 35.

The capacity of the memory 34 must be suificient to bridge the dead time for reversing the direction of motion of the band; it is possible to use a plurality of memories in order to obtain an adequate storage capacity.

Extraction from the memory 34 of the information corresponding to signals 13a, 13b, and so on, is controlled by extraction signals in the form of periodic electrical impulses schematically represented by a dotted-dashed line 37. Signals 37 are generated at the frequency of passage of needle jacks 4 past a selection member 7 so that control information for each selection station is extracted from the memory at exactly the same frequency as the frequency of pasage of elements to be controlled past a selection station. Generation of the signals 37 is achieved by a stationary photo-electric cell 38 actuated by the light beam of a light-source 39 which passes through perforations 40 regularly spaced on a disc 41. The disc is rotated to intermittently cut the light beam by means of a pinion 42 meshing with toothing on the principal crown 43 of the knitting machine.

After extraction thereof from the memory 34, the information corresponding to signals 13a, 13b, and so on, passes to an amplifier 44 and then to the coils of the corresponding electro-magnetic selecting members 7a, 7b, and so on, which selectively act on the needle jacks 4 controlling actuation of the corresponding needles 3.

The pilot signals 35 and the periodic extraction signals 37 are simultaneously fed to an electronic counter 45.

The counter 45 pennanently quantitatively compares the number of signals 35 and 37 and controls the supply to motor 23 along wires 46 and 47 to thereby monitor the speed of the motor 23, and consequently the speed of film 8 past reading device 33, as a function of the amount of information stored in memory 34. For this purpose, any means well known in the art can be incorporated in counter 45 so as to control the speed of the D.C. motor 23 as a function of both the input along wires 24/25 and the quantity of information in the memory 34 as computed by the counter. This monitoring takes place so that the amount of information stored in the memory 34 may vary between a minimum value and a maximum value whereby the memory neither has insufficient information (from the point of view of operation of the knitting machine) nor an excess of information (from the point of view of the capacity of the memory).

In the variant shown in FIGS. 4 to 6, the means for alternately driving and winding the film, and arrangement of the reading means differ considerably from those of the abovementioned example.

For the sake of simplification, the same reference numerals have been used to designate the same parts: thus, as before, a film 8 has longitudinal tracks 13 storing information, in this example by transparent or opaque zones, from which signals 13a, 13b, and so on, are generated and stored in a memory 34 from where they pass either to an amplifier 44 or to a counter 45 to monitor (servocontrol) the speed of a film-driving motor 23.

The signals generated in proportion to the frequency of passage of the jacks 4 past a selecting member 7 are indicated by a dashed-dotted line 48 and can be produced, as in the preceding example, by a mechanism (not shown) linked to operation of the knitting machine, or by any other means.

0n the shah 49 of the motor 23 is mounted a driving disc 50. A second disc 51 is freely mounted on an axle 52 in line with the shaft 49 but mounted on a casing 53 fixed to the housing of the motor 23.

Openings 54 are provided in the casing 53 to enable the application of two pressure rollers 56, 57 against the peripheries of discs 50 and 51 by means of springs schematically indicated by 58. Two further openings 55 in the casing 53 enable the insertion of lighting and reading devices which will be described further on. The film 8 is arranged such that it can be driven and guided by its lateral edges, in either direction, by tangential contact between the peripheral edges of the discs 50 and 5 1, which it partially covers, and the pressure rollers 56, 57.

A light-transmitting channel 59 is inserted between the discs 50 and 51 through an upper opening 55 and projects a narrow light beam from a light source 61 onto the inner face 60 of the film 8.

The reading of the information takes place on the outer face of the film by means of an optical reader 62 comprising as many light-transmitting channels as the film has longitudinal tracks to be scanned. The optical signals collected by the reader 62 during motion of the film are transmitted to a corresponding set of photo-electric cells located in a casing 63, where they are converted into electrical impulses and then delivered to and stored in memory 34.

The film 8 is alternately wound and unwound between two hubs 64 and 65 fixed to the shafts of two individual motors 66 and 67 located on either side of the motor 23.

As for the preceding example, the control of the reversing of the direction of rotation of the motor 23 as well as of the individual motors 66 and 67 can be ensured by reversing signals carried by the film 8.

One possibility is to feed the individual motors 66 and 67 with a voltage of the same sign corresponding to one direction of motion of the film; the respective values of the applied feed voltages, according to the direction of motion of the film, being sufficiently large for the winding motor so as to enable it to wind the film supplied at the maximum speed of the servooperated motor 23 as well as for the largest dimensions of the wound film, and sufiiciently low for the unwinding motor so as to enable it to allow unwinding of the film while exerting a slight braking action thereon.

The film 8 can additionally comprise, before the reversing information for operation of motor 23, pre-reversing information so that, before each reverse of direction of motion, the feed voltage of the individual motors 66 and 67 can be switched off which causes the formation of slack sections of film so as to reduce the inertia at the moment of reverse of the direction of rotation of the servo-operated motor 23.

Between the pressure rollers 56, 57 and the winding/unwinding hubs 64 and 65 the film is constrained to adopt a path passing around rollers 68 and 69 freely mounted on flexible anns 70 and 71 respectively. These arms are not pivoted but are in a supple material such as rubber so that they absorb the differences in tension on the film 8 either at the moment of reversal or during motion. The variation in the position of the rollers 68 and 69 upon flexing of the arms can advantageously be used to control the individual motors 66 and 67 so as to maintain the tension of the film 8 as constant as possible.

F IG. 7 schematically represents a particular arrangement of information on a program film to enable it to be read in the two directions of motion.

The program film 8 comprises a series of longitudinal tracks 1 to 12 each corresponding to a given selection station of the knitting machine; the information stored on each track must be scanned for each cycle of the two alternate winding-up operations.

The information corresponding to positive orders, i.e., the actuation of the needles, is schematically represented by white squares and the information corresponding to negative orders is schematically represented by hatched squares, referred to as "black" for the sake of convenience.

The information on each track is placed on the film according to an alternating formation, namely that the bits of information A,, A,, A,, A, are read in the direction of motion of the film indicated by arrow A the alternated bits of information R,, R R R, being read in the direction of motion of the film indicated by arrow R.

A supplementary track B comprises, at each end of the film, information to control reversal of the direction of rotation of the driving means; a second supplementary track B, is also provided and carries, just before the reversal information, prereversal information to control the winding means, as previously described.

An auxiliary track T of pilot information comprising a continuous series of alternating transparent and opaque zones, the spacing of which is identical to that of the principal information, is schematically represented by white and hatched (black) surfaces. Successive orders for reading the principal information are supplied by this pilot track upon the transition from black to white or vice-versa, but always the same transition being used for both directions of motion of the film. In the illustrated example, the transition black-white is chosen.

The light-transmitting channels C of the stationary optical reader 62 are located in a fixed position transversally of the film and so that one channel is allocated per track.

Each transition from black to white, that is, each edge of the transition zones represented by the white and hatched (black) surfaces, of the pilot track T is located on the axis of a m versal row of principal information. Thus, when a transversal row of information is located in line with the transversal line of channels C, a reader CT for the track T detects a transition edge from the black to white surfaces and triggers reading of the information on the other tracks at the precise moment when a transversal row of information is aligned for reading.

It is understood that in the illustrated position, reading of information on the transversal row aligned with channels C will be triggered for movement of the film in the direction A (transition from black to white), but not for movement of the film in the direction R (transition from white to black).

By means of this particular arrangement of pilot information, and because of the fact that triggering of the reading orders by the reader CT of the pilot information is only carried out upon the transition from black to white, there is thus obtained, systematically and without possible staggering, a discrimination between the information which must be read for one direction of motion of the film and the information which must be read for the opposite direction of motion.

Upon reversal of the direction of motion of the film, the changeover from the reading of rows A to the reading of rows R thus takes place automatically, without the need for accessory means for registering the direction of motion or for staggering of the film in relation to its driving means.

what is claimed is:

l. A circular knitting machine comprising a plurality of elements to be controlled movable past at least one selecting member, and means for selectively actuating each selecting member comprising a tape having first and second ends carrying a program of information, a first member supporting the first end of the tape and a second member supporting the second end of the tape, means for alternately winding the tape along a path onto one of the first and second members and unwinding the tape from the other of the first and second members, reading means adjacent the path of the tape, means for storing information from the reading means, means for extracting information from the storage means in the order of reading at a frequency equal to the frequency of passage of elements past each selection member and for transmitting this information to the selecting member(s), means for quantitatively comparing the input of information to the storage means with the output of information from the storage means, and a reversible variable speed motor for regulating the speed at which the tape passes the reading means, the speed of the motor being servo-controlled as a function of the quantity of information in the storage means so that the rate of reading information on the tape need not be synchronized with the frequency of passage of the elements past each selecting member.

2. A knitting machine as claimed in claim 1, in which the first and second members are driven by individual first and second motors, and in which the tape carries information for the control of reversal of the servo-controlled motor and prereversal information for cutting off supply to the individual motors before each reversal, whereby slack sections are formed on the tape to reduce the inertia thereof at the moment of reversal.

3. A knitting machine as claimed in claim 2, in which the first and second individual motors are fed at different voltages of the same sign corresponding to the direction of motion of the tape, the feed voltage for the first or second motor acting as a winding motor being larger than the feed voltage for the first or second motor acting as an unwinding motor, and the feed voltage for the unwinding motor being such that the unwinding member exerts a slight braking efiect on the tape.

4. A knitting machine as claimed in claim 1, comprising at least one driving disc driven by the servo-controlled motor, and a plurality of pressure rollers urging the tape into tangential driving contact with a part of the periphery of the or each driving disc.

5. A knitting machine as claimed in claim 1, comprising a driving disc driven by the servo-controlled motor, an idling disc mounted coaxially with the driving disc, and a pair of pressure rollers urging the longitudinal edges of the tape into tangential contact with a part of the peripheries of the discs, whereby the tape and idling disc are driven by the driving disc.

6. A knitting machine as claimed in claim 5, in which the program tape is a film comprising a plurality of longitudinal tracks carrying information in the form of transparent or opaques zones arranged into transversal rows, a number of tracks equal to the number of selecting members carrying information for control of the selection members, and comprising lighting means for delivering a beam of light between the discs onto the internal face of the film passing over the peripheries of the discs, the beam of light being dimensionned to cover a single transversal row of zones aligned therewith, optical reading means comprising a plurality of light-transmitting channels located to receive luminous signals though the film upon passage of successive transversal rows of information past the light beam, the number of channels being equal to the number of longitudinal tracks on the film, and photo-electric cells for each of the channels corresponding to a track carrying information for control of the selection members, the photo-electric cells being adapted to receive the luminous signals and transmit corresponding electrical signals to the storage means.

7. A knitting machine as claimed in claim 1, in which the program tape comprises a plurality of longitudinal tracks carrying information for control of the selection members in the form of transparent or opaque zones arranged into transversal rows, and an auxiliary track carrying a succession of transparent and opaque zones, the length of the auxiliary zones corresponding to the separation of adjacent transversal rows of information, and auxiliary reading means for the auxiliary track for selectively controlling the reading of alternate transversal rows of information according to the direction of motion of the tape.

8. A knitting machine as claimed in claim 7, in which the auxiliary reading means actuates reading of a transverse] row of information upon passage by the auxiliary reading means of a transition edge from one of the transparent or opaque auxiliary zones to the other, whereby for one direction of motion of the film a first set of transition edges actuates reading of first transversal rows of information and for the other direction of motion of the film a second set of transition edges actuates reading of second transversal rows of information alternating with the first rows.

9. A circular knitting machine comprising a plurality of elements to be controlled movable past at least one selecting member, and means for selectively actuating each selecting member comprising a tape carrying a program of information, means for driving the tape along a path and for winding the tape, reading means adjacent the path of the tape, means for storing information from the reading means, means for extracting information from the storage means in the order of reading at a frequency equal to the frequency of passage of elements past each selection member and for transmitting this information to the selecting member(s), counter means for quantitatively comparing the input of information to the storage means with the output of information from the storage means, and variable speed motor means for regulating the tape driving means as a function of the quantity of information in the storage means as computed by said counter means so that the speed of driving of the tape and consequently the rate of reading information on the tape need not be synchronized with the frequency of passage of the elements past each selec tion member.

I l i i l 

1. A circular knitting machine comprising a plurality of elements to be controlled movable past at least one selecting member, and means for selectively actuating each selecting member comprising a tape having first and second ends carrying a program of information, a first member supporting the first end of the tape and a second member supporting the second end of the tape, means for alternately winding the tape along a path onto one of the first and second members and unwinding the tape from the other of the first and second members, reading means adjacent the path of the tape, means for storing information from the reading means, means for extracting information from the storage means in the order of reading at a frequency equal to the frequency of passage of elements past each selection member and for transmitting this information to the selecting member(s), means for quantitatively comparing the input of information to the storage means with the output of information from the storage means, and a reversible variable speed motor for regulating the speed at which the tape passes the reading means, the speed of the motor being servo-controlled as a function of the quantity of information in the storage means so that the rate of reading information on the tape need not be synchronized with the frequency of passage of the elements past each selecting member.
 2. A knitting machine as claimed in claim 1, in which the first and second members are driven by individual first and second motors, and in which the tape carries information for the control of reversal of the servo-controlled motor and pre-reversal information for cutting off supply to the individual motors before each reversal, whereby slack sections are formed on the tape to reduce the inertia thereof at the moment of reversal.
 3. A knitting machine as claimed in claim 2, in which the first and second individual motors are fed at different voltages of the same sign corresponding to the direction of motion of the tape, the feed voltage for the first or second motor acting as a winding motor being larger than the feed voltage for the first or second motor acting as an unwinding motor, and the feed voltage for the unwinding motor being such that the unwinding member exerts a slight braking effect on the tape.
 4. A knitting machine as claimed in claim 1, comprising at least one driving disc driven by the servo-controlled motor, and a plurality of pressure rollers urging the tape into tangential driving contact with a part of the periphery of the or each driving disc.
 5. A knitting machine as claimed in claim 1, comprising a driving disc driven by the servo-controlled motor, an idling disc mounted coaxially with the driving disc, and a pair of pressure rollers urging the longitudinal edges of the tape into tangential contact with a part of the peripheries of the discs, whereby the tape and idling disc are driven by the driving disc.
 6. A knitting machine as claimed in claim 5, in which the program tape is a film comprising a plurality of longitudinal tracks carrying information in the form of transparent or opaques zones arranged into transversal rows, a number of tracks equal to the number of selecting members carrying information for control of the selection members, and comprising lighting means for delivering a beam of light between the discs onto the internal face of the film passing over the peripheries of the discs, the beam of light being dimensioned to cover a single transversal row of zones aligned therewith, optical reading means comprising a plurality of light-transmitting channels located to receive luminOus signals though the film upon passage of successive transversal rows of information past the light beam, the number of channels being equal to the number of longitudinal tracks on the film, and photo-electric cells for each of the channels corresponding to a track carrying information for control of the selection members, the photo-electric cells being adapted to receive the luminous signals and transmit corresponding electrical signals to the storage means.
 7. A knitting machine as claimed in claim 1, in which the program tape comprises a plurality of longitudinal tracks carrying information for control of the selection members in the form of transparent or opaque zones arranged into transversal rows, and an auxiliary track carrying a succession of transparent and opaque zones, the length of the auxiliary zones corresponding to the separation of adjacent transversal rows of information, and auxiliary reading means for the auxiliary track for selectively controlling the reading of alternate transversal rows of information according to the direction of motion of the tape.
 8. A knitting machine as claimed in claim 7, in which the auxiliary reading means actuates reading of a transversal row of information upon passage by the auxiliary reading means of a transition edge from one of the transparent or opaque auxiliary zones to the other, whereby for one direction of motion of the film a first set of transition edges actuates reading of first transversal rows of information and for the other direction of motion of the film a second set of transition edges actuates reading of second transversal rows of information alternating with the first rows.
 9. A circular knitting machine comprising a plurality of elements to be controlled movable past at least one selecting member, and means for selectively actuating each selecting member comprising a tape carrying a program of information, means for driving the tape along a path and for winding the tape, reading means adjacent the path of the tape, means for storing information from the reading means, means for extracting information from the storage means in the order of reading at a frequency equal to the frequency of passage of elements past each selection member and for transmitting this information to the selecting member(s), counter means for quantitatively comparing the input of information to the storage means with the output of information from the storage means, and variable speed motor means for regulating the tape driving means as a function of the quantity of information in the storage means as computed by said counter means so that the speed of driving of the tape and consequently the rate of reading information on the tape need not be synchronized with the frequency of passage of the elements past each selection member. 